Combustion chamber and method for supplying fuel to a combustion chamber

ABSTRACT

The combustion chamber has a body with nozzles to inject a fuel to be burnt therein. The nozzles define a plurality of groups to be fed in parallel. The nozzles of each group define at least two stages that are differently operated according to the different operating conditions. The combustion chamber also has a manifold for collecting a fuel to be distributed among the groups, a plurality of supply elements distributing the fuel originating from the manifold to each group, for each group, splitters for diverting the fuel coming from the supply elements between the stages.

RELATED APPLICATION

The present application hereby claims priority under 35 U.S.C. Section 119 to European Patent application number 10194320.7, filed Dec. 9, 2010, the entire contents of which are hereby incorporated by reference.

FIELD OF INVENTION

The present invention relates to a combustion chamber and a method for supplying fuel to a combustion chamber. In particular, reference to a combustion chamber of a gas turbine is made.

BACKGROUND

Combustion chambers are known to comprise a body into which fuel and an oxidiser (typically compressed air) are injected to be combusted and generate hot gases that are expanded in a turbine.

Typically, in order to comply with emissions (NO_(x), CO, uncombusted hydro carbon), pulsations, power optimisation, etc, the fuel is supplied into the combustion chamber via a plurality of stages.

Each stage (typically comprising a plurality of nozzles) allows a fuel to be injected within the combustion chamber in a particular position according to the current load.

With reference to FIG. 1, a traditional premixed combustion chamber 1 is shown.

The premixed combustion chamber 1 has mixing devices 2 into which fuel is supplied and mixed with the compressed air to form a mixture that in burnt into a combustion device 3.

Each mixing device 2 has a plurality of stages identified by 4 a, 4 b, 4 c (any number of stages is anyhow possible, often they are between two and four) each typically comprising a plurality of nozzles.

In order to supply fuel to these stages, a supply circuit 5 is provided, having manifolds 7 a, 7 b, 7 b for each stage and connected to a main line 8 a, 8 b, 8 c supplying fuel into it; in addition control valves 9 a, 9 b, 9 c are provided, to regulate the fuel flow to the manifolds 7 a, 7 b, 7 c.

During operation the fuel is supplied to the manifolds 7 a, 7 b, 7 c that distribute it.

In particular the mass flow distribution among the stages 4 a, 4 b, 4 c is controlled via the valves 9 a, 9 b, 9 c.

Even if largely used, this structure implies structural and operating constrains.

Structural Constrains

The supply circuit 5 with a manifold for each stage is complex and expensive; in particular the most expensive components are the manifolds 7 a, 7 b, 7 c, which are made up of rings running over the whole combustion chamber circumference, and the valves 9 a, 9 b, 9 c.

Operational Constrains

Operation during transient periods is very complex, since the three valves 9 a, 9 b, 9 c must be regulated at the same time; in some cases this regulation can cause instabilities and, in extreme cases, it can also cause flame extinction.

In addition, when one (or more) of these valves 9 a, 9 b, 9 c is closed, the relative manifold 7 a, 7 b, 7 c must be purged with air. During the following operation the air contained within the manifold becomes hot and when the valve must be opened to supply fuel within the manifold again, it is necessary to purge the same manifold with air before fuel is introduced within it (to avoid risks of explosions). For this reason, when the valve is opened, first air enters the combustion chamber and only afterwards the required fuel is injected. It is clear that in some cases this air injection could be very troubling; for example, in case of operation close to the lean blow off, flame extinction could occur.

In addition, when the valves 9 a and/or 9 b and/or 9 c are open, in case their regulation must be changed (for example to counter pulsations or increase flame stability), time is required for the fuel pressure to be adjusted over the whole manifolds 7 a and/or 7 b and/or 7 c and up to the injectors 4 a, 4 b, 4 c; this time interval increases the time required for the regulation.

SUMMARY

The present disclosure is directed to a combustion chamber having a body with nozzles to inject a fuel to be burnt therein. The nozzles define a plurality of groups to be fed in parallel, and the nozzles of each group define at least two stages, that are differently operated according to the different operating conditions. The combustion chamber includes a manifold for collecting a fuel to be distributed among the groups, a plurality of supply elements distributing the fuel originating from the manifold to each group; and at least one splitter associated with each group for diverting the fuel coming from the supply elements between the stages.

In another aspect, the disclosure is directed to a method for supplying fuel to a combustion chamber having a body with nozzles to inject a fuel to be burnt therein. The nozzles define a plurality of groups to be fed in parallel, and the nozzles of each group define at least two stages, that are differently operated according to the different operating conditions. The method includes collecting in a manifold the fuel to be distributed among the groups and distributing the fuel originating from the manifold to each group via supply elements. The method also includes diverting, for each group, the fuel coming from the supply elements between the stages.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will be more apparent from the description of a preferred but non-exclusive embodiment of the combustion chamber and method, illustrated by way of non-limiting example in the accompanying drawings, in which:

FIG. 1 is a schematic view of a traditional combustion chamber;

FIGS. 2 through 5 schematically show different embodiments of the invention;

FIG. 6 schematically shows an embodiment of the invention implemented in a premixed combustion chamber;

FIG. 7 schematically shows an embodiment of the invention implemented in a diffusion combustion chamber; and

FIG. 8 schematically shows a further embodiment of the invention implemented in a premixed combustion chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Introduction to the Embodiments

An aspect of the invention therefore includes providing a combustion chamber and a method by which the combustion chamber is simpler and the operating constrains are reduced.

Another aspect of the invention is to provide a combustion chamber wherein the fuel response to valve regulation is very quick.

These aspects are attained by providing a combustion chamber and a method in accordance with the accompanying claims.

DETAILED DESCRIPTION

With reference to the figures, these show a combustion chamber 10 having a body with nozzles to inject a fuel to be burnt therein.

The nozzles define a plurality of groups 13 to be fed in parallel, and the nozzles of each group 13 define at least two stages 12 a, 12 b (each stage 12 a, 12 b generally includes a plurality of nozzles; additional stages in addition to the two stages 12 a, 12 b described can also be provided, i.e. any number of stages is possible); the stages 12 a, 12 b are differently operated according to the different operating conditions, for example load.

In addition, a manifold 14, typically in the form of a ring, that collects the fuel to be distributed between the stages 12 a, 12 b of the groups 13 is provided; advantageously one single manifold 14 is provided, alternatively also more than one manifold can be provided, in this case at least one manifold 14 feeds different stages of different groups.

Connected to the manifold 14, supply elements 15 that distribute the fuel originating from the manifold 14 to each group 13 are provided.

In addition, for each group 13, one or more than one splitter 17 (according to the distribution scheme) for diverting the fuel coming from the supply elements 15 between the stages 12 a, 12 b is also provided.

One main line 19 to supply fuel into the manifold 14 is provided, the main line 19 has a control valve 20 to regulate the fuel flow within the manifold 14.

For each group 13, each supply element 15 is defined by a duct, and further ducts 22 are provided between the splitters 17 and the nozzles of each stage 12 a, 12 b (FIGS. 2 and 3).

Splitters 17 can have different configurations, but in all cases they divert the fuel flow between the stages 12 a, 12 b but cannot control the total flow (i.e. the fuel flow is only regulated via the valve 20).

In an embodiment (FIG. 3) the splitters 17 comprise a control valve 25 on each duct 15, 22, operated by an actuator 26; preferably the actuator 26 is a common actuator (i.e. a single actuator operating all the valves 25 of the particular splitter 17).

In a different embodiment (FIG. 2) the splitters 17 comprise a multiple-way control valve 28 to which the ducts 15, 22 are connected.

The number of stages can also be greater than only two (FIGS. 4 and 5).

In this case a plurality of supply elements 15 are provided for each group 13, each supply element 15 being connected to another supply element 15.

In particular FIGS. 4 and 5 show examples with different configurations of the splitters 17 already shown in FIGS. 2 and 3; it is clear that any configuration is possible, that the splitter used can be the same in all cases or different and each of the splitter 17 shown and described can be located upstream or downstream of the other according to the particular needs.

The splitters 17 can be locally controlled, for example they can be controlled on the basis of the fuel pressure within the duct 15 that carries them.

Alternatively the splitters 17 can be centrally controlled, i.e. they can be all connected to a control unit that drives them according to the different operating conditions such as, for example, load.

In both cases the following control schemes are possible:

-   -   open loop control that adjusts the fuel distribution according         to fixed or variable boundary conditions (for example burner         position within the combustion chamber, operating condition such         as load, load gradient, ambient conditions, fuel quantity, flame         temperature, etc).     -   closed loop control that adjusts the fuel distribution according         to a measured parameter (for example emissions, pressure         fluctuation, pressure drop, flame temperature, material         temperature, fuel composition, etc).     -   mixing devices-to-mixing device difference control, i.e. the         operating differences among mixing devices can be pre-defined as         a function of given operating parameters (from open loop         controllers) or measured parameters (from closed loop         controllers) or can be self-adjusting based on optimisation         algorithms linked to a closed loop control.

Naturally, also combinations of locally and centrally controlled splitters 17 are possible.

The operation of the combustion chamber is apparent from that described and illustrated and is substantially the following.

In the following reference to the embodiment of FIG. 4 is made, operation of different embodiments is similar and not described in detail.

Fuel is supplied via line 19 and valve 20 into the manifold 14; the valve 20 regulates the fuel flow, i.e. the amount of fuel that enters the manifold 14 and that is distributed among the groups 13.

From the manifold 14 the fuel enters the supply elements 15 and reaches the first splitters 17.

Each first splitter 17 can:

-   -   divert the whole fuel to the duct 22 and, thus supply the whole         fuel to the first stage 12 a;     -   divert the whole fuel to the second supply element 15 downstream         of the supply element 15 directly connected to the manifold 14.         Since the second supply element 15 is also provided with a         splitter 17, the fuel is then diverted to a duct 22 that feeds         the second stage 12 b and/or to another duct 22 that feeds the         third stage 12 c;     -   divert a part of the fuel to the duct 22 and thus to the first         stage 12 a and a part of the fuel to the second supply element         15 downstream of the supply element 15 directly connected to the         manifold 14. Also in this case, the fuel is then diverted         between a duct 22 that feeds the second stage 12 b and/or         another duct 22 that feeds the third stage 12 c.

It is clear that by appropriately diverting the fuel at the splitters 17, the required fluid distribution among the stages 12 a, 12 b, 12 c for each particular load can be achieved. Advantageously, the combustion chamber in embodiments of the invention is simple, because the most troubling and expensive component are the manifold and the valve 20; the splitters 17 and their control system are not troubling and are generally cheap.

In addition operation is much simpler than with traditional combustion chambers. In fact only one single valve 20 controls the fuel flow within the combustion chamber, thus regulation of a plurality of valves that control the amount of fuel flow to a plurality of manifolds is avoided.

In addition, since the splitters 17 only control the fuel distribution among the stages, the fuel amount to each group 13 is in all cases regulated via the valve 20, i.e. defective controls and risks of providing a fuel amount too large or too low is avoided.

Moreover, during operation the valve 20 is always open (because when it is closed no fuel reaches the nozzles and the flame extinguishes), no manifold purging with air is thus necessary; this further simplifies the structure and reduces possible troubling operating conditions that could be caused by air that enters the combustion chamber when fuel is required instead.

Advantageously, since the fuel regulation is made downstream of the manifold 14, the regulation is very quick.

During operation, it is not mandatory that the staging of different groups of nozzles be the same; i.e. the staging can be the same for all groups of it can be different.

In the following, an example of locally controlled splitters is described.

In this case, each supply element 15 receives (almost) the same amount of fuel; then the splitters 17, on the basis of local conditions that may be different over the circumference of the combustion chamber, regulate the staging, i.e. the amount of fuel supplied to each stage of the group.

In the following an example of centrally controlled splitters is described.

Also in this case each supply element 15 receives (almost) the same amount of fuel; then the splitters 17, on the basis of a signal provided by the control unit, regulate the staging, i.e. the amount of fuel supplied to each stage of the group.

In the following three schematic examples of a premixed combustion chamber (FIG. 6), a diffusion combustion chamber (FIG. 7), and a different premixed combustion chamber (FIG. 8) are described.

The premixed combustion chamber (FIG. 6) has a combustion device 30 (for example with an annular shape) with mixing devices 31 connected upstream of it.

The mixing devices 31 can be made up of two or more shells defining a cone swirl space; the shells define slots for air introduction within the cone swirl shape. A lance is housed within the cone swirl space.

A first stage 12 a is for example defined by nozzles provided at the lance (for example at the tip of the lance, it could be a pilot stage) and a second stage 12 b is defined by the nozzles at the shells.

As schematically shown, one single ring shaped manifold 14 is provided with one single supply line 19 and valve 20.

From the manifold 14 the supply elements 15 extend and are connected to the splitters 17; from the splitters 17 the ducts 22 that feed the first and second stages 12 a, 12 b depart.

In this embodiment the nozzles of each group 13 belong to the same mixing device 31.

FIG. 7 shows a diffusion combustion chamber with a combustion device 30 that is for example annular in shape. Nozzles are connected to the combustion device 30 defining the stages 12 a, 12 b, 12 c; also in these cases (even if mixing devices are not provided and the nozzles directly face the combustion device 30) the stages 12 a, 12 b, 12 c are grouped in groups 13.

As shown, the ring shaped manifold 14 is provided connected to a line 19 provided with the valve 20. From the manifold 14 the supply elements 15 depart, each connected to a first splitter 17 that supplies fuel to a duct 22 feeding the first stage 12 a and a further supply element 15 connected downstream of the first splitter 17. This further supply element 15 is connected to a further splitter 17 that fees two ducts 22 connected to the second stage 12 b and third stage 12 c.

Naturally also different types of combustion chambers are possible, for example a can combustor combustion chamber can implement the structure and the method in embodiments of the present invention.

FIG. 8 shows an example in which a group 13 includes the stages of a plurality of mixing devices 31.

Each mixing device 31 has the same features already described with reference to the first example and FIG. 6. In this example, the combustion chamber has four stages 12 a through 12 d.

In particular two stages 12 a and 12 b are common to two of the mixing devices 31 of each group 13, and one single mixing device has a third and fourth stage 12 c and 12 d; therefore during operation the two mixing devices operated in common can for example generate a flame with a higher temperature and the other mixing device a flame with a lower temperature. Naturally in different embodiments the groups 13 can include any number of mixing devices operated in common with flame having a higher temperature and any number of mixing device operated with a flame at a lower temperature and the number of stages of each burner can also be any, for example only one. A possible embodiment is thus a combustion chamber with the features shown in FIG. 8, wherein the mixing devices 31 have only one stage (i.e. the mixing devices 31 could have only the stages 12 a and 12 c; in this case each mixing device or group of mixing devices 31 defines a stage).

The present invention also refers to a method for supplying fuel to a combustion chamber.

With reference to FIG. 2, the method comprises:

-   -   collecting the fuel to be distributed among the groups 13 in the         manifold 14,     -   distributing the fuel originating from the manifold 14 to each         group 13 via a supply element 15;     -   for each group 13, diverting the fuel coming from the supply         elements 15 between the stages 12 a, 12 b (and possible further         stages).

It should be understood that the features described may be independently provided from one another.

In practice, the materials used and the dimensions can be chosen at will according to requirements and to the state of the art.

REFERENCE NUMBERS Prior Art

-   -   1 combustion chamber     -   2 mixing devices     -   3 combustion device     -   4 a, 4 b, 4 c nozzles     -   5 supply circuit     -   7 a, 7 b, 7 c manifolds     -   8 a, 8 b, 8 c main lines     -   9 a, 9 b, 9 c control valves

Embodiment of the Invention

-   -   10 combustion chamber     -   12 a, 12 b, 12 c, 12 d stages     -   13 groups     -   14 manifold     -   15 supply element     -   17 splitters     -   19 main line     -   20 control valve     -   22 ducts     -   25 control valve     -   26 actuator     -   28 multiple way control valve     -   30 combustion device     -   31 mixing device 

1. Combustion chamber having a body with nozzles to inject a fuel to be burnt therein, wherein: the nozzles define a plurality of groups (13) to be fed in parallel, and the nozzles of each group (13) define at least two stages (12 a, 12 b, 12 c, 12 d), that are differently operated according to the different operating conditions, the combustion chamber comprising: a manifold (14) for collecting a fuel to be distributed among the groups (13), a plurality of supply elements (15) distributing the fuel originating from the manifold (14) to each group (13); and at least one splitter (17) associated with each group for diverting the fuel coming from the supply elements (15) between the stages (12 a, 12 b, 12 c, 12 d).
 2. The combustion chamber according to claim 1, further comprising a plurality of supply elements (15), each supply element (15) being connected to another supply element (15).
 3. The combustion chamber according to claim 1, wherein one main line (19) to supply fuel into the manifold (14) is provided, the main line (19) having a control valve (20) to regulate the fuel flow within the manifold (14).
 4. The combustion chamber according to claim 1, wherein each splitter (17) can only divert the fuel flow among the stages (12 a, 12 b, 12 c, 12 d).
 5. The combustion chamber according to claim 1, wherein, for each group (13), each supply element (15) is defined by a duct, and further ducts (22) are provided between the splitters (17) and the nozzles of each stage (12 a, 12 b, 12 c, 12 d), the splitters (17) comprise a control valve (25) on each duct operated by an actuator (26).
 6. The combustion chamber according to claim 5, wherein the actuator (26) is a common actuator.
 7. The combustion chamber according to claim 1, wherein for each group (13), each supply element (15) is defined by a duct, and further ducts (22) are provided between the splitters (17) and the nozzles of each stage (12 a, 12 b, 12 c, 12 d), the splitters (17) comprise a multiple-way control valve (28) to which the ducts are connected.
 8. The combustion chamber according to claim 1, wherein the splitters (17) are locally controlled.
 9. The combustion chamber according to claim 8, wherein the splitters (17) are controlled on the basis of a fuel pressure within the duct that carries them.
 10. The combustion chamber according to claim 8, wherein the splitters (17) are controlled on the basis of an open loop control or closed loop control scheme.
 11. The combustion chamber according to claim 1, wherein the splitters (17) are centrally controlled.
 12. The combustion chamber according to claim 11, wherein the splitters (17) are controlled on the basis of an open loop control or closed loop control scheme.
 13. The combustion chamber according to claim 1, wherein the combustion chamber is a premixed combustion chamber having mixing devices (31) and at least one combustion device (30), wherein the nozzles of each group (13) belong to same mixing device (31).
 14. Method for supplying fuel to a combustion chamber having a body with nozzles to inject a fuel to be burnt therein, wherein: the nozzles define a plurality of groups (13) to be fed in parallel, and the nozzles of each group (13) define at least two stages (12 a, 12 b, 12 c, 12 d), that are differently operated according to the different operating conditions, the method comprising: collecting in a manifold (14) the fuel to be distributed among the groups (13), distributing the fuel originating from the manifold (14) to each group (13) via supply elements (15); diverting, for each group (13), the fuel coming from the supply elements (15) between the stages (12 a, 12 b, 12 c, 12 d). 